If you subscribe at the normal rate (not this discounted rate), the cost is about the same as purchasing every upgrade was before. What a lot of people used to do, though, was to only upgrade every 2 or 3 versions because usually the number of new features in a given update was not enough to justify the cost. So this way is more expensive for those people.

Where the new model really shines is for those who need a particular product only for a couple of months at a time. I had a freelance project last year for which I needed Premiere and After Effects CS6, but I couldn't justify an upgrade for that one project. Paying $90 for two months of access was very easy, and I could easily bill that amount to the client. Likewise, I was working for a small start-up that did not want to pay for full licenses, so we had five AE subscriptions. Over the course of a year, we paid about what it would have cost to buy them outright, but it helped the company with cash flow, and when production slowed down, we could cut the number of licenses we were paying for.